Some recipes say a cube is an inch on all sides, others say smaller.
Guessing from experience, that probably gives 1-2 tablesppons paste or could be replaced (not exact same taste) by 1 teaspoon dried.
Alternatives:
1) order fresh ginger, cut in chunks, store in freezer (lasts for months).
2) if the recipe has sweet notes, use crystalized ginger, which will give you sugar but also some of the bite of the original.
Even if you like ginger and are converting it to another format for this recipe, start with the smaller end of the conversion factors. It's sometimes impossible to fix a dish with too much (salt, ginger, whatever) but you can always add more.